svn commit: r362794 - head/sys/compat/linuxkpi/common/include/linux

[Hans Petter Selasky]

Author: hselasky
Date: Tue Jun 30 08:41:33 2020
New Revision: 362794
URL: https://svnweb.freebsd.org/changeset/base/362794

Log:
  Document the is_signed(), type_max() and type_min() function macros in the
  LinuxKPI. Try to make the function argument more readable.
  
  Suggested by:	several
  MFC after:	1 week
  Sponsored by:	Mellanox Technologies

Modified:
  head/sys/compat/linuxkpi/common/include/linux/kernel.h

Modified: head/sys/compat/linuxkpi/common/include/linux/kernel.h
==============================================================================
--- head/sys/compat/linuxkpi/common/include/linux/kernel.h	Tue Jun 30 07:37:24 2020	(r362793)
+++ head/sys/compat/linuxkpi/common/include/linux/kernel.h	Tue Jun 30 08:41:33 2020	(r362794)
@@ -564,20 +564,33 @@ linux_ratelimited(linux_ratelimit_t *rl)
 #define	__is_constexpr(x) \
 	__builtin_constant_p(x)
 
-#define	is_signed(x) (((x)-1 / (x)2) == (x)0)
+/*
+ * The is_signed() macro below returns true if the passed data type is
+ * signed. Else false is returned.
+ */
+#define	is_signed(datatype) (((datatype)-1 / (datatype)2) == (datatype)0)
 
-#define	type_max(x) (						\
-  (sizeof(x) >= 8) ? (is_signed(x) ? INT64_MAX : UINT64_MAX) :	\
-  (sizeof(x) >= 4) ? (is_signed(x) ? INT32_MAX : UINT32_MAX) :	\
-  (sizeof(x) >= 2) ? (is_signed(x) ? INT16_MAX : UINT16_MAX) :	\
-		     (is_signed(x) ? INT8_MAX : UINT8_MAX)	\
+/*
+ * The type_max() macro below returns the maxium positive value the
+ * passed data type can hold.
+ */
+#define	type_max(datatype) ( \
+  (sizeof(datatype) >= 8) ? (is_signed(datatype) ? INT64_MAX : UINT64_MAX) : \
+  (sizeof(datatype) >= 4) ? (is_signed(datatype) ? INT32_MAX : UINT32_MAX) : \
+  (sizeof(datatype) >= 2) ? (is_signed(datatype) ? INT16_MAX : UINT16_MAX) : \
+			    (is_signed(datatype) ? INT8_MAX : UINT8_MAX) \
 )
 
-#define	type_min(x) (					\
-  (sizeof(x) >= 8) ? (is_signed(x) ? INT64_MIN : 0) :	\
-  (sizeof(x) >= 4) ? (is_signed(x) ? INT32_MIN : 0) :	\
-  (sizeof(x) >= 2) ? (is_signed(x) ? INT16_MIN : 0) :	\
-		     (is_signed(x) ? INT8_MIN : 0)	\
+/*
+ * The type_min() macro below returns the minimum value the passed
+ * data type can hold. For unsigned types the minimum value is always
+ * zero. For signed types it may vary.
+ */
+#define	type_min(datatype) ( \
+  (sizeof(datatype) >= 8) ? (is_signed(datatype) ? INT64_MIN : 0) : \
+  (sizeof(datatype) >= 4) ? (is_signed(datatype) ? INT32_MIN : 0) : \
+  (sizeof(datatype) >= 2) ? (is_signed(datatype) ? INT16_MIN : 0) : \
+			    (is_signed(datatype) ? INT8_MIN : 0) \
 )
 
 #endif	/* _LINUX_KERNEL_H_ */